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By T. R. Lippard

PURE gypsum may be broken down into its constituents as follows: [ ] Standard specifications (ASTM Designation C22-25) state that a material shall not be considered gypsum if it contains less than 64.5 pct by weight of CaS042H2O. Anhydrite, the second calcium sulphate mineral found in nature, may be broken into its constituents as follows: [ ] PROPERTIES OF GYPSUM AND ANHYDRITE Pure gypsum is colorless to white but various impurities change its color to shades of gray, brown, red, or pink. It has a hardness of 2 in the Mohs scale and can be scratched with the fingernail. The specific gravity of pure gypsum is 2.3 to 2.4, so that rock gypsum, free from moisture, weighs about 145 lb per cu ft. Gypsum crystallizes in the monoclinic system in tabular crystals that exhibit good cleavage

Jan 1, 1949

By L. S. Allen, R. L. Caldwell, W. R. Mills

Borehole models used in the study of nuclear well logging are reviewed and the merit of heterogeneous us homogeneous formation simulation is discussed. .A heterogeneous model for simulating sandstone formations of variable porosity is described. Simulation adequacy was checked by steady-state and pulsed-neutron measurements. INTRODUCTION In the course of developing new methods of nuclear well logging, the problem of testing new logging instruments under controlled conditions always arises. This testing is usually done in wells of known lithology, porosity and fluid saturation, or in laboratory test facilities which simulate the borehole environment. Although the former approach is possibly more satisfying, it is frequently difficult or inconvenient to find wells with enough variation in the cited parameters for a truly comprehensive study, On the other hand. laboratow- test facilities can simulate a wide variety of formation and borehole conditions if care is exercised to maintain adequate simulation under all conditions. Workers concerned with the development of nuclear well logging methods have reported several types of research facilities in the past. Tittle, et a1 used cubical tanks filled with Ottawa silica sand to study the steady-state behavior of thermal and epithemal neutrons in simulated sandstone logging environments.1 In addition to the effects of fresh vs salt water, a wide variety of casing sizes and compositions were investigated. Tittman also used a large tank of Ottawa sand to measure the slowing down length of sio2;2 for making the same measurement in CaCO3, however, an assembly of solid Vermont marble blocks was used. More recently a very useful and carefully planned test pit for nuclear logs was constructed under the auspices of the API.3 This facility consists of three massive limestone sections, each 6-ft thick and more than 5 ft in diameter. The blocks are buried, one on top of the other, in a concrete- lined pit having a total depth of 24 ft. Each section is made of a different limestone to achieve porosity variation, the selection being Carthage (2 per cent), Indiana (19 per cent) and Austin (26 per cent). The blocks are traversed by a 7 7/8-in. diameter borehole and are saturated with fresh water. Great care was taken to insure total saturation of the stone. Homogeneous mixtures and materials have not been used exclusively for simulating earth formations. Tittle, et a1 4 showed that a heterogeneous lattice of water and graphite could be used to simulate Liquid furfural with very little effecton measured thermal and epi thermal neutron distributions. Subsequently, a lattice-type model for simulating limestone earth formations was designed and built by Berry This limestone model was constructed of 7/8- x 11/4- x 36411. marble rods glued together with a plastic resin to form a 36-x 42- x 42in. cube. The cube was honeycombed vertically with 7/8- x 7/8- x 3641-1. holes for porosity and had a 111/2-in. diameter hole in the center to serve as the borehole. Lower porosities were simulated by placing marble rods in the square holes. The finished cube was used with the borehole vertical and set in a tank to hold liquid for filling the holes in the rock matrix. A second type of heterogeneous borehole model has been proposed by Kukharenko, et a1.6= In this concept the model is composed entirely of solid material. The hydrogen equivalent of formation fluids is simulated by making the model of alternating layers of dense rock and celluloid. Additional hydrogen is included by drilling vertical holes in the rock sections and filling them with solid forms of hydrogeneous material. The volume of the holes is equal to the volume of the celluloid layers, so an axial and radial dispersion of the hydrogeneous material is thus obtained. One such model was composed of alternate 50 mm-thick sand layers and 2 mm-thick celluloid sheets. Approximately 200 appropriately spaced plastic tubes were used in each sand section. The plastic tubes were filled with paraffin for additional hydrogen concentration. This arrangement yielded a model with a water-equivalent hydrogen concentration of 10 per cent. Experimental data taken in this model and in a model consisting of the same material but homogeneously dispersed showed that the heterogeneous system adequately

Jan 1, 1966

By FRANK COLE

THE territory covered in this discussion includes all the states west of the Mississippi river. Agriculture is expanding each year in this section, but until recent years the application of commercial fertilizers as an aid to crop production was not practised to any great extent. The use of commercial fertilizers has increased somewhat, but is still on a small basis as compared with the tonnages used else- where in the United States. During 1928 these western states used 665,100 tons of all classes of fertilizer as compared 'with 7,933,600 tons used in the whole United States; or this western area, compromising near- ly two-thirds the land area, uses about 5 per cent of the total fertilizer. To show how large a tonnage one state may consume, North Carolina for the year 192s used 1,349,360 tons of commercial fertilizer or about twice the amount used by 22 western states.

Jan 1, 1930

By Chung Yu Wang, Guy C. Riddle

There are found in nature upward of II2 minerals containing antimony, but only a few of them, listed in Table I, can be considered as antimony ore-forming minerals. Stibnite (Sb2S3), antimony sulphide or glance, is the principal ore of antimony. The oxide ores—cervantite, kermesite, valentinite, sernarmontite—occur sparingly in nature. Dry methods are generally adopted for the extraction of the metal. Electrometal-lurgical methods have had much attention in America and Germany and have not yet found, on economic grounds, practical or extended application, except in a few places. During recent years, treatment of the poor grades of the ore, especially sulphide, by ore-dressing methods, has commanded some attention and been adopted at a few plants. The impure sulphide of antimony, resulting from the liquation process, is called lLneedle," "liquated" or "crude" anti- mony, and the refined metal itself is called antimony "regulus." The different processes for the treatment of antimony ores are shown in the diagram of Fig. I. Liquation of Crude Antimony The first step in the smelting of antimony is a simple one, the process of LLliquation," which produces crude or needle antimony. Ores containing $ 50 per cent Sb are used in the liquation process for the production of crude. The temperature required for liquation is between 550' and 600°C. Ores to be liquated are broken to about walnut size. If the pieces are larger than this, the low heat used will not penetrate' effectively, and if they are smaller the ore tends to pack too closely for adequate penetration. A packed charge also prevents the free escape of the fused sulphide. Intermittent Liquation in Crucibles The unique type of furnace that is in use in China for smelting is not highly efficient but is simple in construction and operation. The furnace is generally built

Jan 1, 1944

By J. Parke Channing

ALTHOUGH the original thought of investigating waste in industry came from a mining engineer, Herbert Hoover, and although the chairman of that committee was a mining engineer (although the real work was done by the vice-chairman, L. W. Wallace), it is an interesting commentary that when the report first saw light, at St. Louis, on the first of June, 1921, some people most violently went up in the air when it was submitted by the representatives of the mining engineers. At the time they resented most markedly the report of the committee that 50 per cent. of the waste in industry, or as Mr. Ingalls in his paper has properly said, inefficiency in industry, was to be laid upon management. The reason for that seems to have been that, as a whole, the mining industry is pretty well organized and is superior to a large number of manufacturing industries including those studied by the Report. However, this very meeting shows that even the min-ing engineers have finally realized that there is waste or inefficiency in mining and that a large proportion of it can, with propriety, be assessed against management.

Jan 3, 1922

CONTENTS PAGE BARTON, D. C.-The Eötvös Torsion Balance Method of mapping Geologic Structure (T. P. No. 50) 1 GEORGE, P. W.-Experiments with Eötvös Torsion Balance in the Tri-State Zinc and Lead District (T. P. No. 65). 15 LANCASTER-JONES, E.-The Computation of Eötvös Gravity Effects (T. P. No.75) HEILAND, C. A.-A Cartographic Correction for the Eötvös Torsion Balance-(T. P. No. 52) 17 SLICHTER; L. B.-Certain Aspects of Magnetic Surveying (T. P. No. 120). . . . 18 WEAVER, W.-Certain Applications of the Surface Potential Method (T. P. No.121) LUNDBERG, H.-Recent Results in Electrical Prospecting for Ore (T. P. No. 98). . 20 HOTCHKISS, W. 0., ROONEY, W. J. and FISHER, J.-Earth-resistivity Measure-ments in the Lake Superior Copper Country (T. P. No. 82) 21 LEONARDON, E. G. and KELLY, S. F.-Some Applications of Potential Methods to Structural Studies (T. P. No. 115) 23 MASON, M.-Geophysical Exploration for Ores (T. P. No. 45) 25 The Eötvös. Torsion Balance Method of Mapping Geologic Structure Discussion of the paper of D. C.. Barton, issued as Technical Publication No. 50 with Mining and, Metallurgy, February, 1928. D. C. BARTON.-The field surveys which I have been privileged to use as illustrations for this paper were done for Mr. DeGolyer's companies and were released through his favor. W. J. MILLARD, Tulsa, Okla.-Has any oil been found by the torsion balance in West Texas? D. C. BARTON.-NO new oilfield has been discovered on the basis of torsion balance work. It has had some part in controlling the policy of certain companies in playing the extension of known oil fields. A number of "T. B." structures have been drilled and dry holes obtained. Of those known to the writer, one apparently was a structural high, one is a broad general high but locally low and probably is a deep-seated structural high, one seems normal although the control is poor, and one was considered structurally low but is now suspected by some geologists of being structurally high. E. L. DEGOLYER, New York, N. Y.-A large gravity structure, generally referred to, I believe, as the Crosby County Structure, has been found in West Texas. This structure is perfectly symmetrical with the arrows all pointing toward a common center, very much like the Nash salt-dome pattern in Dr. Barton's paper (Fig. 9). One of the peculiar things about it, from the standpoint of the gravity high, is that it is so

Jan 1, 1928

By George Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable appara-tus, which can rapidly give a sufficiently reliable indication of the rela-tive dust hazard.

Jan 1, 1937

Jan 1, 1951

By A. M. E. Eilers

No one who has visited our Western mining districts, and studied the economical part of the beneficiation of the ores occurring all over that vast extent of country, can underrate the high importance of the above subject. By far the larger number of the districts which contain smelting ores, i.e., argentiferous and auriferous lead, or copper ores, are situated in the Great Basin, that great plateau between the Rocky Mountains on the east, and the Sierra Nevada on the west, almost the whole of which is comprised at present in the boundaries of Nevada, Utah, and part of Arizona. This region is essentially a barren country. The extreme dryness of the atmosphere permits but a scanty vegetation in the plains ; and even in the detached mountain-chains running through it-generally from N. to S., or from N. W. to S. E.-there are no trees found except dwarfed pines and mahogany, at the head of sheltered ravines, and a few cottonwoods and willows, which fringe the insignificant streams, before the water sinks in the arid plains. Nearly all the mountain-chains in this region are rich in silver ores. That class of these ores which is adapted to amalgamation, and rich in silver, has been worked with profit for more than ten years. But before the advent of the transcontinental railways, mining was restricted to these ores alone, and the consumption of fuel could be met with the scanty supply of forest trees in the immediate vicinity of the mining districts. Since, however, the Union and Central Pacific Railroads have brought the Great Basin nearer to the commercial centres of the East and the Pacific coast, thus reducing the expenses of freight and labor materially, other silver deposits, containing poorer ores in greater abundance, have been rapidly taken

Jan 1, 1873

By Chas. H. Behre, Arbiter. Nathaniel

Two outstanding factors characterize most undertakings in the mineral industries: (1) mineral deposits are not equally distributed over the earth but are localized by natural processes, and (2) the mineral industries are largely based upon wasting assets. Neither of these factors is invariably true, for a few mineral materials, such as water, are essentially world-wide and others are replaced periodically by processes not unlike crop production. Indeed, with some, such as the salts in the sea, the supply is cyclic in short or long periods, whereas others, like water, though locally or periodically in short supply, are essentially inexhaustible. But to the extent that most minerals are limited to certain areas and are "permanently" consumed, any industry founded upon them, by implication, demands great care in planning for the most effective extraction-the essence of wise and conservative expenditure. Several less unusual yet also truly fundamental factors in the economics of the mineral industry are those involving (1) the various kinds and properties of mineral materials, which influence their use; (2) their geo- logic and geographic availability; and (3) the techniques unique to their discovery, exploration, and utilization. This chapter is designed primarily as a brief background for later ones and as a summary of the several un- usual or at least special factors and of their effect upon the economics of the mineral industry. The social and political and especially the economic aspects of the industry are the main subjects of this volume and are dealt with in extended fashion in subsequent chapters. Fundamental Characteristics of Mineral Deposits DEFINITIONS Minerals are naturally occurring compounds of nonliving matter, each technically defined as having (1) a chemical composition that may vary

Jan 1, 1959

By R. H. Hawkins

An investigation of the applicability of geophyiical methods to northern Ontario lignite deposits was undertaken early in 1930 by the Ontario Research Foundation at the request of the Ontario Department of Mines Pre-Cambrian ... Syenite, granite gnciss, etc. Igneous intrusivcs . Lamprophyre dikes cut the Abitibi River and lover formntions. (Permission of Ontario Dept. of Mines) and was financed in part from a research grant made by the latter organization. The work to date has included gravitational, magnetic and electrical resistivity studies. The gravitational and magnetic measure-

Jan 1, 1934

By J. W. Powell, F. H. Spedding

A complete review of the use of chelating agents in the sepa ration of rare earths by ion-exchange is given as well as a concise description of the recent pilot-plant operations of the Ames Laboratory. The two chelating agents which show the greatest promise are ethylenediamine-N,N,N',N'-tetraacetic acid and N'-(2-hydroxyethyl)ethylenediarnine-N,N,N '-triacetic acid. The first successful separations of rare earths by ion exchange were reported in a collection of papers which appeared in the November, 1947, issue of the Journal of the American Chemical Society.1'9 Some of this work was performed at the Ames Laboratory of the A.E.C., the remainder at the Oak Ridge National Laboratory. The processes developed at Oak Ridge, as well as some of the early Arnes methods, employed 5 pct citric acid-ammonium citrate eluant at low pH and were carried out on either H+-state or NH:-state resin beds. These techniques were successful for the separation of small quantities of either naturally occurring or radioactive rare earths and are still used for the isolation of rare-earth activities from fission products. Concentrated citrate is not economical, however, for use in moderate or large-scale rare-earth separations. For this reason, the Ames Laboratory turned its attention to lower concentrations and higher pH's in order to make more effective use of the eluting agent.10-14 Although elutions have been performed successfully over a wide range of conditions, 0.1 pct citrate at a pH of 8.0 is highly recommended for use on H+-state resin beds.15,16 Elu-tion with 0.1 pct citrate in the pH range from 5 to 9 brings about the separation of the constituent rare earths into a series of flat-topped elution bands which progress down the resin bed, head to tail, without actually pulling apart as do the rare-earth peaks which develop when trace quantities are eluted with 0.25M (5 pct) citrate at low pH's. Because of this, elution with 0.1 pct citrate at pH 8.0 do not produce pure rare earths unless sufficient quantities are present to provide developed bands which are at least several inches long on the columns. Although other eluting agents have proved more effective than citrate solutions, articles concerning the use of citric acid for separating rare earths still appear in the literature occasionally. For example, Ketelle and Boyd17 reported some further studies on the separation of rare earths with 5 pct citrate in 1951. They used 270 to 325 mesh Dowex-50 columns at 100°C and a pH of 3.28. vickery18 compared the effectiveness of a number of eluants for the separation of rare earths on NH+4 state Dowex-50 in 1952. He found that citric acid was more efficient than acetic, malic, tartaric, and aminoacetic acids. In 1953, Mayer and Freiling18 reported that citrate was inferior to malate, glycolate, lactate, and EDTA for the resolution of Sm-Eu and Y-Tb mixtures on 250 to 500 mesh, NH+4-state, Dowex-50 at 87°C. pinta20 used 5 pct citrate in the pH range 2.8 to 3.4 to obtain some rare earths for analytical work the same year. Trombe and Loriers21 reported the use of citric acid in their laboratory to separate rare earths in kilogram quantities. Lariers and Quesney22 reported some separations with citrate in 1954. They used 5 pct citrate at pH 2.8 to separate yttrium and the yttrium-group rare earths from the cerium-group rare earths. briers23 used 5 pct citrate at pH 3.2 and 90°C as late as 1956 to isolate thulium in fair purity. For the separation of tracer quantities of rare earths, Mayer and Freiling19 have recommended pH 5.00, 0.24M lactate at 87 °C on 250 to 500 mesh, NH+4-form Dowex-50. Freiling and Bunney24 have also employed lactic acid for the separation of fission-product rare earths. Cunninghame, Size-land, Willis, Eakins, and Mercer25 have reported a 4-hr separation of Y, Eu, Sm, Pm, Nd, and Pr with 1M lactic acid at pH 3.25 on Zeokarb-225 at 87°C. Stewart, et al.,26 reported separation factors for rare earths distributing between Dowex-50 and 0.25M glycolic acid. stewart27 also reported a 30-61 separation of Y, Tm, Er, Tb, and Lu tracers with buffered, 0.25M glycolic acid containing 0.05 pct Aerosol OT. The resin bed was 400-mesh Dowex-50 (X12). The pH of the ammonia-buffered eluant was 3.5. Various aminopolyacetic acids have also been used to obtain varying degrees of separation of the rare earths. In 1951, Fitch and Russell28 investigated iminodiacetic acid (IDA) and nitrilotriacetic

Jan 1, 1960

DISCUSSION, M. Cohen presiding A. H. Geisler and D. L. Martin (GeneTal Electric Research Laboratory, Schenectady, N. Y.)—We were rather interested to note the author's conclusion that the cubic to tetragonal transformation may be of the second order, for we have been able to show that the order-disorder transformation in an analogous alloy system is a first-order transformation with a discon-

Jan 1, 1952

By George W. Harris

In the earlier period of anthracite-mining, much coal was wasted, both underground and in the culm-banks on the surface. Such waste is common in the development of new mining-districts, in which, as a rule, only the richest material can be profitably treated. In the anthracite-region, special causes operated to increase this evil. The mines were generally worked under 20-year leases, and royalties were paid upon such coal only as was actually marketed. The lessees consequently cared for immediate profit solely. They were not bound to win all the coal they exposed, or to leave it in such condition that their successors could win it. Nor was it their interest or duty to educate consumers in the use of their product. The market called for coal of large sizes; and such coal they furnished, throwing away the rest. Any pains taken by them to bring about a more rational use of coal by their consumers would have borne fruit, after their leases had expired, to the benefit of somebody else. A full statement of the situation was given in 1893, in the report of the State Commission, appointed in 1889 to investigate the subject.' That body included the names of Heber S. Thompson, William Griffith and the late Eckley B. Coxe.2 Its report gives special attention to the utilization of the old culm-banks.

Jan 1, 1906

By A. T. Aldred

HIS note reports the existence of several new scandium intermetallic compounds of the A2B and AB stoichiometries where the A element is scandium and the B element is from group VIII or IB of the periodic table. Alloys were arc melted from high-purity materials using 2-g charges. Typical lot analyses for the materials used are given in Table I. Chemical analyses were not made on the alloys as there was little or no weight loss on melting. After annealing the specimens for 14 days at 600°C and water quenching, metallographic and X-ray techniques were used to determine the occurrence of the various phases. Table II lists the relevant data for the A2B phases. The Ti2Ni structure,2 has ninety-six atoms in a face-centered cubic cell, whilst the Al2Cu structure is body-centered tetragonal.3 The occurrence and stability of the various A2B type phases in transition metal alloy systems has recently been considered by Nevitt.4 The Ti2 Ni-type phases occur over a relatively narrow range of radius ratios from 1.14-1.26 with A partners mainly from the titanium group and B partners predominantly from the cobalt group. This suggests that both a favorable relative size of the atoms and a favorable electron concentration are necessary conditions for the existence of this structure type. A12Cu-type phases involving Ti group elements as A partners are formed with B partners from the cobalt and nickel groups, predominantly the latter, and have a higher radius ratio (1.27-1.29) than the Ti2Ni-type phases. The occurrence of both Sc2Pd and Sc2Co can be rationalized in terms of these considerations but SczNi is anomalous because of its high radius ratio. The radius ratios are calculated from the Goldschmidt CN12 radii and it might be postulated that the scandium atom is reduced in size in the compound. Unfortunately the apparent atomic size of scandium in the compound cannot be calculated from a knowledge of the structure and lattice dimensions. The crystal structure of the Sc2Au compound could not be identified from the powder diffraction pattern, but it is interesting to note that it is isostructural with a series of A2Au phases where A is a rare earth element.5 Pertinent information concerning the AB phases found in this investigation is given in Table 111. All the phases have the ordered bcc CsCl structure. The occurrence and stability of CsC1-type phases have recently been discussed by Dwight,7 who concludes that the relative sizes of the atoms do not appear to be a controlling factor (the radius ratios of all the known phases vary between 0.985 and 1.439) but that the occurrence of the phase is predominantly dependent on the relative positions of the A and B partners in the periodic table. As a measure of the stability of a given CsCl phase it has been customary to define a lattice contraction on alloying, DAB — dAB, where DAB is the AB interatomic spacing as calculated from the Goldschmidt CN8 radii and dAB is the AB interatomic distance in the compound (= v3/2 ao). Values of the parameter DscB -dScB for the compounds found in this investigation are given in column 5 of Table III and are plotted in Fig. 1. If the lattice contraction does in fact reflect the stability of a phase then Fig. 1 shows two very interesting trends when the position of the B partner in the periodic table is considered. Firstly, within any given group the stability increases in order on going from the first to third long period. Secondly, within any given period the stability increases in order as the B partner is taken from the copper, nickel, and cobalt groups. In the case of the second long period, the lattice contraction reaches a maximum at ScRh and then decreases to ScRu. The same trend could

Jan 1, 1962

By Henry M. Howe

Jan 1, 1909

By R. W. Vander Laan

Conneaut has a long and illustrious history as a major Great Lakes port for coal and iron ore. The first dock was built in 1892 for unloading iron ore from the Mesabi Range for shipment to the Pittsburgh steel mills via the Shenango & Lake Erie Railroad, later to become the Bessemer & Lake Erie Railroad. The Pittsburgh & Conneaut Dock Company was incorporated in 1893. The world's first Hulett automatic ore unloader was constructed at Conneaut in 1899. Steam operated, it was the model for the giant electric Huletts used today, named after its inventor, George Hulett, who was a Conneaut resident.

Jan 3, 1974

By Clarence Zener

Contents Page General Principles................................................................. 551 Equilibrium Diagrams......................................................... 551 Nucleation................................................................... 553 Kinetics of Phase-boundary Propagation......................................... 553 Kinetics of Growth of New Phase............................................... 556 Spheroidization............................................................... 560 Pure Iron-carbon System........................................................... 561 Formation of Pearlite.......................................................... 561 Interlamellar Spacing........................................................ 562 Pearlite C-curve............................................................. 563 Bainite Formation............................................................. 565 Formation of Martensite....................................................... 570 Loss of Tetragonality of Martensite.............................................. 570 Effect of Alloys upon Decomposition of Austenite..................................... 572 Pearlite...................................................................... 572 Bainite and Martensite......................................................... 574 Time-temperature-transformation Curves............................................. 576 Appendix A............................................................. ......... 579 Appendix B....................................................................... 580 Appendix C....................................................................... 580 The present investigation started in an attempt to understand certain details of the decomposition of austenite, and of the effect of alloying elements thereon. As the investigation proceeded it became apparent that not only these details, but all the general features of austenite decomposition, could be understood in terms of fundamental physical principles. Since the direct applicability of these physical principles has not been previously recognized, it was decided to incorporate the original results of the investigation into a review of the general subject of the kinetics of austenite decomposition. This review constitutes the present article. An extended summary of the results is given on pages 576 to 579. This article, which deals with the kinetics of phase transformations, may appropriately be considered as a sequel to two recent articles1,2 from this laboratory on the equilibrium relations in medium alloy steels.

Jan 1, 1947

By Clarence Zener

Contents Page General Principles................................................................. 551 Equilibrium Diagrams......................................................... 551 Nucleation................................................................... 553 Kinetics of Phase-boundary Propagation......................................... 553 Kinetics of Growth of New Phase............................................... 556 Spheroidization............................................................... 560 Pure Iron-carbon System........................................................... 561 Formation of Pearlite.......................................................... 561 Interlamellar Spacing........................................................ 562 Pearlite C-curve............................................................. 563 Bainite Formation............................................................. 565 Formation of Martensite....................................................... 570 Loss of Tetragonality of Martensite.............................................. 570 Effect of Alloys upon Decomposition of Austenite..................................... 572 Pearlite...................................................................... 572 Bainite and Martensite......................................................... 574 Time-temperature-transformation Curves............................................. 576 Appendix A............................................................. ......... 579 Appendix B....................................................................... 580 Appendix C....................................................................... 580 The present investigation started in an attempt to understand certain details of the decomposition of austenite, and of the effect of alloying elements thereon. As the investigation proceeded it became apparent that not only these details, but all the general features of austenite decomposition, could be understood in terms of fundamental physical principles. Since the direct applicability of these physical principles has not been previously recognized, it was decided to incorporate the original results of the investigation into a review of the general subject of the kinetics of austenite decomposition. This review constitutes the present article. An extended summary of the results is given on pages 576 to 579. This article, which deals with the kinetics of phase transformations, may appropriately be considered as a sequel to two recent articles1,2 from this laboratory on the equilibrium relations in medium alloy steels.

Jan 1, 1947

By Philip B. Bucky

[ ] FOREWORD THIS symposium brings together points of view, experiences and ideas on rock bursts from a goodly portion of the globe. Some conceptions, particularly those regarding the necessity of depth, have been fairly well shattered, as we find that they are present in the water tunnels of New York, on the surface at marble quarries in Vermont, and in the coal mines of the United States, as well as in the deep mines of the South African and Kolar gold fields, and in the nickel, copper and gold mines of Canada. Their occurrence under such a variety of conditions is, therefore, a challenge,

Jan 1, 1942